Search results for "microbiology"
showing 10 items of 7546 documents
Dynamic complexities in host-parasitoid interaction
1999
In the 1970s ecological research detected chaos and other forms of complex dynamics in simple population dynamics models, initiating a new research tradition in ecology. However, the investigations of complex population dynamics have mainly concentrated on single populations and not on higher dimensional ecological systems. Here we report a detailed study of the complicated dynamics occurring in a basic discrete-time model of host-parasitoid interaction. The complexities include (a) non-unique dynamics, meaning that several attractors coexist, (b) basins of attraction (defined as the set of the initial conditions leading to a certain type of an attractor) with fractal properties (pattern of…
Environmental Variability and Semelparity vs. Iteroparity as Life Histories
2002
Research on the evolution of life histories addresses the topic of fitness trade-offs between semelparity (reproducing once in a lifetime) and iteroparity (repeated reproductive bouts per lifetime). Bulmer (1994) derived the relationship v+P(A)<1 (P(A) is the adult survival;vb(S) and b(S) are the offspring numbers for iteroparous and semelparous breeding strategies, respectively), under which a resident semelparous population cannot be invaded by an iteroparous mutant when the underlying population dynamics are stable. We took Bulmer's population dynamics, and added noise in juvenile and adult survival and in offspring numbers. Long-term coexistence of the two strategies is possible in much…
Effects of patch number and dispersal patterns on population dynamics and synchrony.
2000
In this paper, we examine the effects of patch number and different dispersal patterns on dynamics of local populations and on the level of synchrony between them. Local population renewal is governed by the Ricker model and we also consider asymmetrical dispersal as well as the presence of environmental heterogeneity. Our results show that both population dynamics and the level of synchrony differ markedly between two and a larger number of local populations. For two patches different dispersal rules give very versatile dynamics. However, for a larger number of local populations the dynamics are similar irrespective of the dispersal rule. For example, for the parameter values yielding stab…
Seed Bank in Annuals: Competition Between Banker and Non-banker Morphs
2002
Seed bank is a plant life history strategy against the unpredictability of the biotic and the abiotic environment. We simulated competition between a seed banking and a non-banking morph of an annual plant. A constant fraction of the banker morph seeds was allocated to the seed bank, where they had a constant mortality and germination rate. All surviving seeds of the non-banker morph germinated in the next generation. The seedlings of both morphs experienced similar density-dependent mortality. Whether one of the morphs wins or the morphs coexist was evaluated from parameter space plots and statistically with logistic regression analysis. All parameters of the model had a significant, nonli…
Recuperación post-nihilista de la intimidad corporal y la persona humana a partir de Nietzsche y Conill
2020
El objetivo de este trabajo es poner en relación el núcleo crítico de la última obra de Je-sús Conill, Intimidad corporal y persona huma-na. De Nietzsche a Ortega y Zubiri1, con la pro-blemática del nihilismo, como estructura que pervive en nuestras sociedades contemporáneas, en especial, en el contexto de las neurociencias, la tecnología y nuestro modo de relación con am-bas. Tras bosquejar a modo de presentación las idea clave del libro, en especial su innovadora con-cepción de la intimidad corporal, recuperaré al-gunas aportaciones de la tematización nietzsche-ana del nihilismo, para mostrar, en tercer lugar, que tras la "muerte de Dios" otras instancias toman su lugar, y que las lógicas…
Stabilization of an enzymatic extract from Penicillium camemberti containing lipoxygenase and hydroperoxide lyase activities
2008
International audience; The stabilization of an enzymatic extract, obtained from Penicillium camemberti containing lipoxygenase (LOX) and hydroperoxide lyase (HPL) activities, was investigated using selected additives. Although the addition of KCl (86%, w/w) to the enzymatic extract decreased slightly (7%) the LOX activity, it increased HPL activity by 2.25 fold; however, the addition of dextran resulted in the inactivation of both enzymatic activities. The stability of the solid lyophilized enzymatic extract was greater in the presence of KCl than that without it, with ∼100% residual activity after 8 and 4 weeks of storage at −80 °C, for LOX and HPL, respectively. The rate constants of ina…
Genome sequence of the pea aphid Acyrthosiphon pisum
2010
The genome of the pea aphid shows remarkable levels of gene duplication and equally remarkable gene absences that shed light on aspects of aphid biology, most especially its symbiosis with Buchnera.
Use of grape racemes from Grillo cultivar to increase the acidity level of sparkling base wines produced with different Saccharomyces cerevisiae stra…
2020
The most important oenological characteristics of high-quality sparkling wines are aromatic aspect, taste persistence, perlage, high levels of acidity and low pH. Due to hot climate and reduced rainfall that characterize Sicily region, white grape varieties such as Grillo cultivar cultivated in this area are characterized by very low concentrations of malic and tartaric acids. Grillo cultivar is characterized by an intense production of raceme grapes with low pH and high content of tartaric and malic acids. These fruits possess the chemical properties useful to increase the amounts of acids in the final wines. With this in mind, the present research was carried out to test the ability of fo…
Changes in the physiological and agricultural characteristics of peat-based Bradyrhizobium japonicum inoculants after long-term storage
2000
International audience; Commercial soybean inoculants processed with sterilised peat and stored at 20 °C for 1–8 years were used as experimental materials to assess the changes in the physiological activity of Bradyrhizobium japonicum after storage. Viable counts decreased and physiological characteristics of the bacterium changed during storage, with an increase in the time taken for colony appearance on a medium without yeast extract, an increase in the lag time for nodule appearance on soybean grown in glass tubes and a decrease in survival on seeds. All the inoculants produced a significant increase in grain yield in a field experiment. The percentage of efficient cells in the field (re…
Self-organized dynamics in spatially structured populations
2001
Self-organization and pattern formation represent the emergence of order in temporal and spatial processes. Self-organization in population ecology is gaining attention due to the recent advances concerning temporal fluctuations in the population size of dispersal-linked subunits. We shall report that spatially structured models of population renewal promote the emergence of a complex power law order in spatial population dynamics. We analyse a variety of population models showing that self-organization can be identified as a temporal match in population dynamics among local units, and how the synchrony changes in time. Our theoretical results are concordant with analyses of population data…